Uniaxial strain study of organic conductors α-(BEDT-TTF)₂MHg(SCN)₄ [M=K, NH₄]

In order to clarify what causes the difference in the electronic properties between K-salt and NH₄-salt, we systematically studied the effects of uniaxial strain on α-(BEDT-TTF)₂MHg(SCN)₄ [M=K, NH₄]. Resistance measurements were performed under the uniaxial strain applied along the a-, b*- and c-axes independently. Superconductivity like NH₄-salt was induced in the K-salt under the the c-axis uniaxial strain, while the density wave state like K-salt was induced in NH₄-salt under the a-axis uniaxial strain. It was found that the ratio of the in-plane lattice constant c/a plays a key role in dominating their electronic properties.